shadow-utils mailbox creation race condition
CERT reported an issue with the way shadow-utils' useradd program
creates the users mail spool file. The file is intially created
improperly which gives it random permissions, owned by root for a
short period of time. It may be possible for a local attacker to get
very lucky and acquire write permissions to a world writable SUID
file.
The upstream fix is here:
http://cvs.pld.org.pl/shadow/src/useradd.c?r1=1.50&r2=1.51
When we patch our packages, we may want to check the return value of
the the fchown and fchmod calls.
This issue also affects RHEL3
This issue also affects RHEL2.1

Created attachment 129979[details]
"#useradd foo" strace output
I patched shadow-utils-4.0.3 from rhel4 and checked return value of fchown and
fchmod.
Can I commit patch to CVS and rebuild shadow-utils in rhel[2.1,3, 4]?

Feel free to apply the patch to CVS, but we won't release an update just for
this issue. We've rated it as having a "low" severity, which means we wait
until there is another more sever issue to fix, releasing both fixes at the same
time.
Thanks.

An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.
http://rhn.redhat.com/errata/RHSA-2007-0276.html

Note

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